Energy assisted magnetic recording (EAMR) or heat assisted magnetic recording (HAMR) technology is intended to be used to increase the areal density of information storage devices such as hard disks. In these assisted recording systems, a laser beam is delivered through an optical waveguide and interacts with a near field transducer (NFT) that absorbs part of the optical energy and forms a very strong localized electromagnetic field in the near field region. When the localized electromagnetic field is close enough to the recording medium, the recording medium absorbs part of the localized electromagnetic field energy and is thereby heated up thermally, which helps to realize the magnetic recording process.
For a typical EAMR system, the light coupler, the waveguide and the NFT are inserted between the reader and the writer of a slider. The light coupled from the attached external source (e.g., laser) propagates along the waveguide, and is concentrated to a small area close to an air bearing surface (ABS) of the slider that is adjacent to the NFT. The NFT is a strong absorber of the light wave at resonant status assisted by a surface plasmon effect, and is capable of squeezing the light energy to a very tiny area (e.g., as small as 40 nanometers). The NFT acts as a relay to deliver the concentrated energy to the tiny area of the recording layer of the media which is only several nanometers away and located within the near-field zone. Temporarily, the media is heated up and becomes magnetically soft thereby allowing the writing field to flip the magnetic storage characteristic of this tiny area to the desired bit data.
When the NFT works properly, the electric field around the NFT is much stronger than that found inside the waveguide. For example, the NFT electric field can be up to 3 times stronger than the waveguide electric field. However, due to the evanescent wave nature of the electric field of the NFT, the electric field drops significantly when it is delivered to the recording layer of the media. On the other hand, the coupling of light energy from the waveguide to the NFT is only a single digit percentage, and most light energy is kept confined inside the waveguide. As a result, an electric field from the waveguide (e.g., lobe) can be delivered to recording layer as well without much decay because of the propagation wave nature of the guided wave. In addition, the field size delivered from the waveguide is much bigger than that from the NFT (e.g., up to tens of times larger). So the energy density within the NFT pin interacting region in the recording layer is much higher than that of the waveguide mode interacting region. However, if the NFT does not function properly, the lobe effect will stand out such that the presence of a substantial lobe at the recording layer of the media can interfere with the energy delivery of the NFT and consequently the ability to properly record information in the media. As such, a system for partially or completely suppressing the lobe impact is needed.